function encode64() {

     // private property
    var  _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";

     // public method for encoding
     this.encode = function (input) {
       var output = "";
       var chr1, chr2, chr3, enc1, enc2, enc3, enc4;
       var i = 0;
       input = _utf8_encode(input);
       while (i < input.length) {
         chr1 = input.charCodeAt(i++);
         chr2 = input.charCodeAt(i++);
         chr3 = input.charCodeAt(i++);
         enc1 = chr1 >> 2;
         enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);
         enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);
         enc4 = chr3 & 63;
         if (isNaN(chr2)) {
           enc3 = enc4 = 64;
         } else if (isNaN(chr3)) {
           enc4 = 64;
         }
         output = output +
         _keyStr.charAt(enc1) + _keyStr.charAt(enc2) +
         _keyStr.charAt(enc3) + _keyStr.charAt(enc4);
       }
       return output;
     }

     // public method for decoding
     this.decode = function (input) {
       var output = "";
       var chr1, chr2, chr3;
       var enc1, enc2, enc3, enc4;
       var i = 0;
       input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");
       while (i < input.length) {
         enc1 = _keyStr.indexOf(input.charAt(i++));
         enc2 = _keyStr.indexOf(input.charAt(i++));
         enc3 = _keyStr.indexOf(input.charAt(i++));
         enc4 = _keyStr.indexOf(input.charAt(i++));
         chr1 = (enc1 << 2) | (enc2 >> 4);
         chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);
         chr3 = ((enc3 & 3) << 6) | enc4;
         output = output + String.fromCharCode(chr1);
         if (enc3 != 64) {
           output = output + String.fromCharCode(chr2);
         }
         if (enc4 != 64) {
           output = output + String.fromCharCode(chr3);
         }
       }
       output = _utf8_decode(output);
       return output;
     }

     // private method for UTF-8 encoding
    var _utf8_encode = function (string) {
       string = string.replace(/\r\n/g,"\n");
       var utftext = "";
       for (var n = 0; n < string.length; n++) {
         var c = string.charCodeAt(n);
         if (c < 128) {
           utftext += String.fromCharCode(c);
         } else if((c > 127) && (c < 2048)) {
           utftext += String.fromCharCode((c >> 6) | 192);
           utftext += String.fromCharCode((c & 63) | 128);
         } else {
           utftext += String.fromCharCode((c >> 12) | 224);
           utftext += String.fromCharCode(((c >> 6) & 63) | 128);
           utftext += String.fromCharCode((c & 63) | 128);
         }

       }
       return utftext;
     }

     // private method for UTF-8 decoding
    var _utf8_decode = function (utftext) {
       var string = "";
       var i = 0;
       var c = c1 = c2 = 0;
       while ( i < utftext.length ) {
         c = utftext.charCodeAt(i);
         if (c < 128) {
           string += String.fromCharCode(c);
           i++;
         } else if((c > 191) && (c < 224)) {
           c2 = utftext.charCodeAt(i+1);
           string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));
           i += 2;
         } else {
           c2 = utftext.charCodeAt(i+1);
           c3 = utftext.charCodeAt(i+2);
           string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));
           i += 3;
         }
       }
       return string;
     }
   }

   export default {
     encode64
   }
